BDNF and Alzheimer disease: We focused on 12 CpG sites in promoter IV of the BDNF gene (Figure 3) as this region has been previously reported as differentially methylated in Alzheimer’s disease and other neurological conditions (Rao et al., 2012; Ikegame et al., 2013; Januar et al., 2015; Kang et al., 2015; Xie et al., 2017).